1. Field of the Invention
The present invention relates to a sheet processing apparatus and an image forming apparatus, and more particularly, to a sheet processing apparatus and an image forming apparatus which include a punching apparatus that performs a punching process for forming a punch hole on a sheet.
2. Description of the Related Art
Some conventional image forming apparatuses, such as duplicating machines, laser beam printers, ink-jet printers, facsimile machines and multifunction peripherals thereof, include a sheet processing apparatus which performs a binding process or a punching process for forming a punch hole, for a sheet on which an image has been formed. In such a sheet processing apparatus, for example, if the punching process is performed for the sheet, a sheet to be conveyed is caused to pass through a punch hole forming position for a punching apparatus once, and then is conveyed in the opposite direction to be returned to the punch hole forming position for the punching apparatus. Then, after the sheet is returned to the punch hole forming position in this way, the punch hole is formed at a central portion in a width direction, which is orthogonal to a sheet conveyance direction, of the sheet, by the punching apparatus (see Japanese Patent Application Laid-Open No. 2006-347678).
Incidentally, in the conventional sheet processing apparatus, and the conventional image forming apparatus including the sheet processing apparatus, there is one sheet conveyance route. Thus, if the sheet is reversed to form the punch hole, a succeeding sheet needs to wait on an upstream side in the sheet conveyance direction in the punching apparatus. Here, if the succeeding sheet is caused to wait at such a position, a waiting space, in which the succeeding sheet is caused to wait, needs to be provided on the upstream side in the sheet conveyance direction. If the waiting space is provided in this way, the size of the sheet processing apparatus is increased.
Moreover, if the waiting space is not provided, in order to secure a punching operation time for the punching apparatus, the image forming apparatus temporarily stops an image forming operation so that the succeeding sheet may not be conveyed to the sheet processing apparatus. Therefore, productivity of the image forming apparatus decreases.
Consequently, the present invention has been made in view of such a current situation, and it is an object of the present invention to provide a sheet processing apparatus which can perform the punching process while suppressing the decrease in the productivity, and an image forming apparatus including the sheet processing apparatus.